code review 4889043: rpc: implement ServeRequest to synchronously serve a si...

src/pkg/rpc/server.go

Index: src/pkg/rpc/server.go
===================================================================
--- a/src/pkg/rpc/server.go
+++ b/src/pkg/rpc/server.go
@@ -394,7 +394,7 @@
 func (server *Server) ServeCodec(codec ServerCodec) {
 	sending := new(sync.Mutex)
 	for {
-		req, service, mtype, err := server.readRequest(codec)
+		service, mtype, req, argv, replyv, err := server.readRequest(codec)
 		if err != nil {
 			if err != os.EOF {
 				log.Println("rpc:", err)
@@ -402,9 +402,6 @@
 			if err == os.EOF || err == io.ErrUnexpectedEOF {
 				break
 			}
-			// discard body
-			codec.ReadRequestBody(nil)
-
 			// send a response if we actually managed to read a header.
 			if req != nil {
 				server.sendResponse(sending, req, invalidRequest, codec, err.String())
@@ -412,37 +409,31 @@
 			}
 			continue
 		}
-
-		// Decode the argument value.
-		var argv reflect.Value
-		argIsValue := false // if true, need to indirect before calling.
-		if mtype.ArgType.Kind() == reflect.Ptr {
-			argv = reflect.New(mtype.ArgType.Elem())
-		} else {
-			argv = reflect.New(mtype.ArgType)
-			argIsValue = true
-		}
-		// argv guaranteed to be a pointer now.
-		replyv := reflect.New(mtype.ReplyType.Elem())
-		err = codec.ReadRequestBody(argv.Interface())
-		if err != nil {
-			if err == os.EOF || err == io.ErrUnexpectedEOF {
-				if err == io.ErrUnexpectedEOF {
-					log.Println("rpc:", err)
-				}
-				break
-			}
-			server.sendResponse(sending, req, replyv.Interface(), codec, err.String())
-			continue
-		}
-		if argIsValue {
-			argv = argv.Elem()
-		}
 		go service.call(server, sending, mtype, req, argv, replyv, codec)
 	}
 	codec.Close()
 }
 
+// ServeSingle is like ServeCodec but synchronously serves a single request

[rsc, 2011/08/15 16:11:09]

suggest ServeRequest instead of ServeSingle.

// ServeRequest serves one request from codec and then returns.
// It does not close the codec.

the part about goroutines is not strictly
relevant: what's relevant is when it returns.

[sougou, 2011/08/15 20:17:18]

Done.

+// without launching a goroutine. It does not close the codec upon completion.
+func (server *Server) ServeSingle(codec ServerCodec) os.Error {
+	sending := new(sync.Mutex)
+	service, mtype, req, argv, replyv, err := server.readRequest(codec)
+	if err != nil {
+		if err == os.EOF || err == io.ErrUnexpectedEOF {
+			return err
+		}
+		// send a response if we actually managed to read a header.
+		if req != nil {
+			server.sendResponse(sending, req, invalidRequest, codec, err.String())
+			server.freeRequest(req)
+		}
+		return err
+	}
+	service.call(server, sending, mtype, req, argv, replyv, codec)
+	return nil
+}
+
 func (server *Server) getRequest() *Request {
 	server.reqLock.Lock()
 	req := server.freeReq
@@ -483,7 +474,38 @@
 	server.respLock.Unlock()
 }
 
-func (server *Server) readRequest(codec ServerCodec) (req *Request, service *service, mtype *methodType, err os.Error) {
+func (server *Server) readRequest(codec ServerCodec) (service *service, mtype *methodType, req *Request, argv, replyv reflect.Value, err os.Error) {
+	service, mtype, req, err = server.readRequestHeader(codec)
+	if err != nil {
+		if err == os.EOF || err == io.ErrUnexpectedEOF {
+			return
+		}
+		// discard body
+		codec.ReadRequestBody(nil)
+		return
+	}
+
+	// Decode the argument value.
+	argIsValue := false // if true, need to indirect before calling.
+	if mtype.ArgType.Kind() == reflect.Ptr {
+		argv = reflect.New(mtype.ArgType.Elem())
+	} else {
+		argv = reflect.New(mtype.ArgType)
+		argIsValue = true
+	}
+	// argv guaranteed to be a pointer now.
+	if err = codec.ReadRequestBody(argv.Interface()); err != nil {
+		return
+	}
+	if argIsValue {
+		argv = argv.Elem()
+	}
+
+	replyv = reflect.New(mtype.ReplyType.Elem())
+	return
+}
+
+func (server *Server) readRequestHeader(codec ServerCodec) (service *service, mtype *methodType, req *Request, err os.Error) {
 	// Grab the request header.
 	req = server.getRequest()
 	err = codec.ReadRequestHeader(req)
@@ -568,6 +590,12 @@
 	DefaultServer.ServeCodec(codec)
 }
 
+// ServeSingle is like ServeCodec but synchronously serves a single request

[rsc, 2011/08/15 16:11:09]

same

[sougou, 2011/08/15 20:17:18]

Done.

+// without launching a goroutine. It does not close the codec upon completion.
+func ServeSingle(codec ServerCodec) os.Error {
+	return DefaultServer.ServeSingle(codec)
+}
+
 // Accept accepts connections on the listener and serves requests
 // to DefaultServer for each incoming connection.  
 // Accept blocks; the caller typically invokes it in a go statement.